This invention is directed to resectoscopes and, more particularly, to an improved electrode assembly for use with resectoscopes. Such electrodes may be monopolar or bipolar. Monopolar probes include a single active electrode introduced into a body cavity to be engageable with and insertable into a tissue portion of the body cavity. A passive electrode is attached to the outer body surface of the patient and a conducting plate is typically adhesively attached to the patient's leg. The patient's body serves to complete the electrical circuit. Tissue ablation and coagulation is achieved by introducing sufficient power into the active electrode. Bipolar electrode probes include both active and passive electrodes that are similarly introduced together into the body cavity and are spaced apart from each other by a predetermined distance. Each electrode is engageable with and insertable into the tissue portion. The electrical circuit is completed by the body tissue disposed between the active and the passive electrodes. However, the construction of such prior art devices do not provide reliability and safety. Many devices include plural joints in the electrical path. Each joint adds resistance to the electrical path. Therefore, the power source is then required to have an initial output voltage to overcome the resistance. This may lead to misfiring or delayed firing.
For example, one known prior art device includes an electrode having a power element and a return element that form a cutting loop. The return element extends from the cutting loop and is spot-welded to a stainless steel sleeve forming an intermediate joint. Proximally to that joint the sleeve is slip fitted to a stainless steel return contact. Both the active and return elements reside in the single lumen formed by the stainless steel sleeve. Because of the sleeve's stainless steel construction the sleeve does not afford flexibility. This device also terminates proximally in a contact in communication with a power source. The contact comprises a straight section of tungsten wire epoxied into a brass fitting. The construction of this device does not provide optimal operation. More specifically, the intermediate joint in the current path formed by the stainless steel sleeve connection with the return element, the lack of separate lumens, and the epoxied wire in proximal contact for the power element cause this device to be more prone to shorting and failure.
Another device is shown and described in U.S. Pat. No. 5,810,764, in which a bipolar loop electrode device for use with a resectoscope is disclosed. In one embodiment, a return electrode is incorporated in the loop electrode assembly as an electrically conducting shaft covered with an insulating layer. The distal end of the shaft is exposed for completing the return path with active electrode assembly. The proximal end is also exposed to connect the electrode to a power supply. The loop portion of the assembly has a proximally extending electrical connection. The connection may be wires, metal tubes, or the like. The electrical connection extends through the shaft to a connector leg at the proximal end of the assembly. The electrical connections are connected to the electrode using crimping, soldering, or welding. This device uses tubing to conduct power making the device stiff causing higher actuation forces in the working element. Additionally, using the tubing to conduct power makes electrical conduction more difficult increasing the chances for misfire or delayed firing.
Another prior art device is shown and described in U.S. Pat. No. 5,976,129, in which a bipolar electrode assembly includes an active electrode loop and a return electrode loop. Each electrode is contained in a separate guide sheath to extend from the distal end of the device to the proximal end to connect to a power supply. The connections for the return and active electrodes are located in a common, two-prong plug. This device uses a roller to coagulate blood after cutting. The device must be energized through an external source. Additionally, this device includes complicated electrical connections that may lead to misfiring and delayed firing.
Another prior art device is shown and described in U.S. Pat. No. 5,201,732, in which a bipolar sphincterotomy device includes a pair of conductive wires. The wires extend from the distal end of the device to provide bipolar electrode surfaces. To prevent shorting, each wire may be disposed in a separate lumen of a flexible elongate tubular member and run as uninterrupted wires from the distal to proximal end of the device. However, this device does not disclose a wire loop and is not suitable for use with a resectoscope. Additionally, the number of electrical connections may increase the risk of misfiring.
Another prior art device is shown and described in U.S. Pat. No. 5,047,027, in which a bipolar electrosurgical device for tumor resection is disclosed. The device has wires that may be disposed in separate lumens of a flexible elongate tubular member and run as uninterrupted wires from the distal to proximal end of the device. The device has an active electrode in the form of a circular loop at the distal end of the device. The return electrode has a spiral wound configuration proximal to the distal electrode. This device poses a shock hazard to the patient because there is nothing to complete the electrical circuit. Furthermore, the device includes electrical connections that increase the risk for misfiring.
Another prior art device is disclosed in U.S. Pat. No. 5,192,280, which shows and describes parallel loop-like bipolar electrodes at the distal end of an electrosurgical device. The device is intended for use in transuretheral resectioning of the prostate. Wires for each electrode pass through a ceramic head member at the distal end of the device and are joined to the electrodes at two points. Proximal to the connection points the wires are disposed in a common lumen. This device is not constructed to perform electrosurgical cutting without secondary movement and is not user friendly.
Another prior art device is disclosed in U.S. Pat. No. 6,471,701, which shows and describes a bipolar electrode assembly for use with a resectoscope. The electrode assembly includes a cutting loop. A convex insulator is mounted between the arms of the loop. The assembly includes a neutral (return) electrode that has an exposed conductive surface. Conductors connect the active and return electrodes to the terminals of the power source. The conductors are contained in the tube forming a single lumen. This device includes multiple contacts increasing the number of joints in the electrical path.
None of the prior art devices disclose a bipolar electrode for use with a resectoscope that provides flexibility yet is constructed to prevent shorting and failure.